1. Field of the Invention
The present invention relates to an apparatus for automatically adjusting the clearance of a support yoke, and more particularly to an apparatus for automatically adjusting clearance of a support yoke, in which a cam, a spacing member, and an elastic member are included, and in a case where a support yoke is worn away due to friction, etc. against a rack bar, while the cam performs relative rotation movement respective to the support yoke by means of an elastic force of the elastic member disposed between the support yoke and the cam, the spacing member pushes the support yoke in a direction of the rack bar so as to maintain a predetermined interval between the spacing member and the support yoke, thereby maintaining clearance of the support yoke in a predetermined degree.
2. Description of the Prior Art
A steering apparatus is an apparatus allowing a driver to change a progressing direction of a vehicle according to the driver's desire, i.e. an auxiliary apparatus which can change a rotation center, about which a front wheel of the vehicle is rotated, so as to allow a vehicle to move in a desired direction.
FIG. 1 is a schematic sectional view of a typical steering apparatus for a vehicle.
As shown in FIG. 1, a conventional steering apparatus includes a steering wheel 100 equipped with a seat, a steering shaft 105 connected with the steering wheel, a steering column 103 allowing the steering shaft to be fixed to a chassis, a gear box 130 including a rack gear 110 and a pinion gear 120 which convert rotational force inputted from the steering shaft 105 to linear movement, a rack bar 140 having an inner ball joint 135 included in both ends thereof, a tie rod 150 formed integrally with a ball of the inner ball joint 135, and an outer ball joint 155 included in an end of the tie rod 150. Also, the tie rod 150 is connected with the knuckle 159 of a tire 158 in such a manner that the tie rod 150 is connected with the outer ball joint 155.
FIG. 2 is a side sectional view of a conventional rack and pinion type gear box. The gear box 130 includes a pinion shaft 276, a rack bar 140, a support yoke 260, a yoke spring 263, a yoke plug 265, and a rack housing 270. The rack and pinion type gear box 130 converts rotational force inputted from the steering shaft 105 to linear movement as described above.
The pinion shaft 276 receives rotational force from an input shaft connected with the steering shaft 105 so as to transfer the rotational force to the rack bar 140. The pinion shaft 276 is connected with the input shaft through a torsion bar, and a pinion gear 120, which is engaged with the rack gear 110, is formed at an end of the pinion shaft 276.
The rack bar 140 is assembled with the pinion shaft 276 so as to convert rotational movement to linear movement. The rack bar 140 has a bar-shape extending between front wheels and has inner ball joints 135 formed at both ends thereof. A rack gear 110, which is engaged with the pinion gear of the pinion shaft 276, is formed between the inner ball joints 135.
The support yoke 260 properly maintains clearance between the rack bar 140 and the pinion shaft 276 so as to allow power to be smoothly transferred. The support yoke 260 is positioned at a side opposite to a surface where the rack gear 110 is formed, which is a rear surface of the rack bar 140, and has a structure which can move in front and rear directions in such a manner that it is inserted into the rack housing 270 having a cylinder.
The support yoke 260 has a cylindrical shape so as to slide in front and rear directions within the cylinder of the rack housing 270, and a front part of the support yoke 260 making contact with the rack bar 140 has a semi-circular shaped groove so as to make close contact with a rear surface of the rack bar 140.
Also, in order to effectively transfer power in such a manner that the rack bar 140 and the pinion shaft 276 make close contact with each other, the yoke spring 263 is disposed at a rear side of the support yoke 260 so as to push the support yoke 260 under a predetermined amount of pressure, thereby compensating clearance generating between the rack bar 140 and the pinion shaft 276.
Such a support yoke 260 has sliding friction against the rear surface of the rack bar 140. Therefore, in order to prevent the rack bar 140 from being worn away or prevent generation of noise due to the friction, a support yoke 260 made from plastic material, which is ductile material in comparison with the rack bar 140, is used.
The yoke spring 263 performs a function for applying pressure so as to allow the support yoke 260 to make close contact with the rack bar 140, and a coil spring is typically used as the yoke spring. The yoke plug 265 is positioned at a rear surface of the yoke spring 263 so as to support the yoke spring 263.
The yoke plug 265 applies pressure to the support yoke 260 in such a manner that the yoke plug 265 supports the yoke spring 263. It is typical that the yoke plug 265 has a male screw-thread so as to be assembled with the rack housing 270 having a female screw-thread. The yoke plug 265 has a groove, into which a wrench can be inserted, formed at a rear surface thereof. Therefore, when the yoke plug 265 is assembled, or clearance is generated between the rack bar 140 and the pinion shaft 276, tension of the yoke spring 263 can be adjusted by tightening the yoke plug 265 by the wrench.
As such, in the structure where clearance between the rack bar 140 and the pinion shaft 276 is compensated in such a simple manner that the conventional support yoke 260 is pressured by the yoke spring 263, there is a gap of about 0.05 mm formed between the yoke plug 265 and the support yoke 260.
However, over long term use, the support yoke 260 moves in a direction of the rack bar 140 so that the gap between the yoke plug 265 and the support yoke 260 increases. As a result, the yoke plug and the support yoke collide with each other, thereby generating noise due to vibration. In order to prevent noise generated due to vibration, the yoke plug 265 has to be again adjusted. Also, replacement of the entire of the steering apparatus is often necessary in a process for maintaining. Therefore, an apparatus, which can automatically compensate clearance without separate adjusting operation, has been required.